This invention relates to a continuous centrifugal thickener advantageously used to thicken sludges such as waste activated sludge discharged from a sewage treatment system.
A continuous centrifugal thickener provided with a rotary barrel of truncated-cone shape having a filter which prevents a passage of solid particles larger than the desired particle size has already been put for practical use. In a well-known thickener, sludge is continuously fed at a predetermined flow rate within a barrel which rotates at high speed on its own axis. This sludge forms a layer rotating with the filter and moving axially from one end on the small-diameter side to the other end on the large-diameter side on the rotating filter, and during movement thereof, a portion composed of water and small particles, that is filtrate, is released by the action of a centrifugal force outside the barrel passing through the filter while the other portion remaining on the filter, that is thickened sludge, is released from the foremost end of the barrel. The efficiency of thickening depends on the magnitude of the centrifugal force acting on the layer of sludge formed on the filter and mesh of the filter. If these factors are not suitably settled, desired degree of thickening can not be achieved.